7. Through Thickness Fracture Behavior of Transversely Graded Ti/TiB Material

Fracture behavior of a Ti/TiB graded material with a crack perpendicular to the gradient direction was investigated. Three-point bending experiment was conducted and full-field displacement fields were measured on both faces of the specimen, metallic and ceramic-rich surfaces, using 2D digital image correlation technique. Stress intensity factors were calculated using the displacement fields obtained on both faces of the specimen, and were compared to the effective fracture toughness determined from fracture load data. The overall fracture toughness was found to be very close to the stress intensity factor determined using the displacement field on ceramic-rich side. However, the stress intensity factors calculated on both surfaces using the displacement fields, showed different values. In addition, scanning electron microscope observations were performed to examine the fracture surface of the material. It was observed that the crack front is inclined, indicating that the fracture may have initiated in the ceramic side and followed by a very fast propagation to the metallic side.